This invention is directed generally to one feature of a pipe or electronic organ, namely, the ability to control the expression of the music being played by varying the volume and timbre of the sound produced. This is usually done by using an “expression shoe,” sometimes referred to as a “swell shoe.” The expression shoe usually controls the volume of the organ sounds. In addition, the expression shoe may control the timbre along with the volume, as well as having one or more additional effects on the sounds produced.
In general, the expression shoe is a control, found on a pipe or electronic organ console, located beneath the keyboards, and usually directly above the pedal board. The expression shoe controls the “expression” or, as more commonly called, the “swell shades.” In a pipe organ, the swell shades are used to vary the size of openings to the pipe chambers, where the organ sounds are produced. The chambers typically house a group of pipes or other sound-producing devices, which can be played from the organ console. Accordingly, the swell shades, which are typically movable “louvers,” are controlled by the organist from the organ console, by moving the expression shoe. The position of the expression shoe therefore represents a relative position of the swell shades. With the shoe in the “closed” position, the swell shades are closed, reducing the amount of sound allowed to escape from the organ chamber. When the shoe is in the “open” position, the pipe chamber is nearly fully exposed, allowing the sounds produced to radiate out of the pipe chamber.
Expression shoe position detection has evolved over the years along with technology. Early systems connected the expression shoe directly to the shades via a mechanical linkage. When organs were first “electrified”, the shoes were connected to a roller contact strip or multi-staged switch. This was typically a mechanical linkage connected from the shoe to a round wooden rod that had a metal contact embedded into the length of the rod on an angle. A multi-finger contact strip was then mounted so that the contact fingers slid on the rod, perpendicular to the length of the rod. As the shoe was moved, the metal contact strip would engage more or fewer of the finger contacts as the rod rotated. Each contact finger was typically connected to a solenoid, which rotated a louver on the expression shades. In some cases the fingers were “summed” to create an “analog” or “staged” input in order to achieve smoother movement of the shade transitions.
In newer systems, the expression shoe position is determined by the use of a mechanical linkage connected to a potentiometer, commonly referred to as a pot. The pot produces a linear signal that represents the shoe's position. This analog signal, typically a voltage, is sent to a control called a swell engine. The swell engine takes the analog signal and produces a motor control signal, which is fed to a motor. The motor, using a mechanical linkage, controls the position of the swell shades. Using this system, the swell shades can be precisely controlled by the expression shoe. Some swell engines are designed to take an analog signal as an input, or a staged input as described above, to provide maximum flexibility.
There are several problems typically associated with the conventional expression shoes of the types described above. In the contact finger systems, the contacts wear and corrode, eventually making them intermittent. Expression shoes using a potentiometer have problems as well. For example, the potentiometer relies on a wiper sliding over wire windings or sliding on a film of a conductor which, after time, becomes dirty or worn causing intermittent “jumps” in the swell shade position when the expression shoe is moved.
Furthermore, expression shoes typically have an adjustable tensioning mechanism in order to provide a “feel.” This mechanism typically relies on a controlled clamping of a control rod to provide the desired degree of resistance to movement. If not properly configured, this mechanism can wear, causing “slop” or an inconsistent feel to the expression shoe's action. Mechanical wear in the potentiometer can also compromise the desired “feel” as set by the latter mechanism.
We realized that there is a need in the organ industry for an expression shoe that will last the lifetime of an instrument without maintenance.
Conventional expression shoes have typically use a number of interconnected brackets to achieve the desired mounting with a structural member or surface of the organ. The fabrication and assembly of this bracket mounting system adds to the overall expense of fabrication of the expression shoe. Moreover, in order to accommodate mounting either to a rail-type member or a flat surface, different bracket arrangements have heretofore been provided. This further adds to the expense of the fabrication of the expression shoe, by requiring that multiple alternative brackets and related assemblies be provided and custom assembled, depending on the requirements for a particular installation.
The expression shoe of the invention has been designed to eliminate or reduce all of these potential problems. A hall-effect system has been chosen to measure the shoe's position, utilizing fixed magnets, without any moving parts. The tensioning mechanism on the expression shoe has been designed with material that has minimal wear and should not require additional adjustment for the life of the shoe after it has been initially set.
The expression shoe of the invention utilizes a novel and improved extruded mounting bracket, requiring a minimum number of fabrication and machining steps as well as a minimum amount of additional mounting hardware. This greatly simplified mounting assembly, using a relatively simply fabricated extrusion overcomes the above-noted problems in conventional expression shoe mounting bracket arrangements.